1. Field of the Invention
The present invention relates to a navigation system and method providing route guidance to a user.
2. Description of the Related Art
As widely used related art for providing a user with route guidance on a navigation system installed in a vehicle, a conventional system receives a destination as a point on a map specified by a user, or a position selected from a list of candidate destination positions registered in advance, sets a guidance route to the received destination, and displays the set guidance route on a map thereby guiding travel along the guidance route.
As related art of setting a guidance route on this type of onboard navigation system, known systems prefer a route which does not cross a lane opposite to a traveling lane, or does not make a U-turn into the opposite lane (See, for example, Japanese Patent Laid-Open Publication No. H6-102051, and Japanese Patent Laid-Open Publication No. H9-210711).
When a user is receiving travel guidance along the guidance route as described above, or the user is not receiving travel guidance, there are often cases that the user wants to move into a lane opposite to a present traveling lane, and to drive back on the path along which the user has just been traveling. These include a case where the user has traveled straight at an intersection at which the user should have turned left or right, and wants to return to the intersection at which the user should have turned left or right; and a case where the user is traveling on an expressway, has passed an exit of the expressway at which the user should have exited to a local road, and wants to return to that exit of the expressway. These also include a case where when the user is traveling while looking for a gas station, the user finds a gas station on the side of the opposite lane, but the user cannot enter the gas station crossing the opposite lane at that position due to a center strip; and a case where the user changes his or her mind, and wants to return to a restaurant after the user has passed that restaurant.
In these cases, though it may be contemplated that the user makes the vehicle U-turn from the traveling lane to the opposite lane, and travels back on the path along which the user has just been traveling, a complicated operation such as driving the vehicle into a clear space on the roadside, turning the vehicle around, and then entering the path by making a turn is necessary to make a U-turn except for a case where a dedicated path for a U-turn is provided. In addition, such a drive operation increases the stress of an ordinary user. Further, it may be impossible to make a U-turn depending on the traveling lane and the surrounding conditions.
On the other hand, instead of making the vehicle U-turn directly from the present traveling lane to the opposite lane, it may be contemplated to drive back on the path along which the user has just been traveling by driving the vehicle while making left and right turns using other paths, thereby moving into the lane opposite to the present traveling lane.
Consequently, in this case, the following problems occur if a user receives travel guidance from the onboard navigation system for a route from a present traveling lane to the opposite lane on a present driving path according to the conventional travel guidance following a guide route.
Namely, though it is first necessary to set a destination to a position on the lane opposite to the present traveling lane on the present traveling path for the user to receive such travel guidance, it is difficult to immediately set the destination by specifying a point on a map. In addition, the user cannot expect that such a position is registered on the list of destination candidates in advance.
Further, when the user sets a destination around the present position to move into the lane opposite to the present traveling lane on the present traveling path, since the present position and the destination are close to each other, the onboard navigation system determines that the vehicle has arrived at the destination, and does not set a guide route as the user expects. Even if the guide route is set, the onboard navigation system determines that the vehicle has arrived at the destination after the start of the route guidance, and terminates the route guidance even if the vehicle has not moved into the lane opposite to the present traveling lane.